that motor, in helicopters, got a bad rap untill someone put another carb on one. The TT36 was the same way untill they started installing a different low-end needle. The problem was that the midrange had an extremely fat spot due to the low-end needle design being very blunt . Sounds like you have that exact problem. I had both engines, and the problem seemed to stem from the low end needle "emerging" from the spraybar right at the midrange setting where you hover. The needles were so blunt, you'd get an extremely rich "burp" right before hover point. I tapered the needle on my 46 with a file, after chucking it up in a drill,..and totally eliminated the problem. Doesn't take much, just a little taper and the transition is smoother, therefore there is not a big "bump" in the mixture at one point. The motor actually ran EXTREMELY well after that,.. sort of a daylight to dark difference.